A. One of the major objectives of this chapter is to maintain and, if possible, improve existing water quality by preventing discharge of stormwater runoff pollutants. In considering issues such as ease of implementation and cost-effectiveness, the following minimum water quality criteria are established to meet the objective of this chapter.
B. Stormwater detention facilities shall include provisions to detain, for extended periods of time, runoff from the water quality design storm (one-year, twenty-four-hour rainfall event), using methodology appropriate for the drainage area under consideration and approved by the Township Engineer.
C. Release of detained stormwater can begin at the start of the storm (i.e., the stormwater detention facility will not permanently retain a portion of the runoff). The design of the facility shall consider and minimize the chances of clogging and sedimentation potential.
D. When detention basins are used to satisfy the water quality requirement, the invert of the water quality orifice may be placed at the invert of the basin. Because the standard for water quality may result in a fairly small outlet orifice in detention basins, the Township Engineer will determine the minimum standard diameter orifice as part of the stormwater management plan review. In soils nonconducive to infiltration, the addition of an underdrain is required, although this requirement can be waived upon determination by the Township Engineer that conditions warrant such a waiver.
E. All stormwater management facilities must implement the water quality requirement of this section. The water quality objective can be obtained through a variety of approved BMP's or combinations thereof, including retention basins, detention basins and bioretention areas.
F. Below-grade detention facilities may not be used to satisfy the water quality requirement. Examples include below-grade infiltration beds or galleries and below-grade detention chambers. In these instances, approved water quality BMP's which supplement the below-grade stormwater detention facilities shall be installed. Examples include water quality inlets (including oil/water separators), filter strips and sand filters. All such water quality BMP's must be designed to treat runoff derived from the water quality design storm (one-year, twenty-four-hour rainfall event).
G. Unless derived from roofs associated with known or suspected contamination, roof runoff is exempt from the water quality requirement. However, this exemption applies only to roof runoff before it is combined with runoff from other sources.
H. Commercial and industrial properties and establishments must demonstrate compliance with the NPDES (40 CFR, Chapter 1, Part 122), as administered by DEP. Copies of stormwater pollution prevention plans (SWPPP) and monitoring reports shall be provided to the Township.